Assessment of bax and bcl-2 immunoexpression in patients with oral lichen planus and oral squamous cell carcinoma.

Lichen planus (LP) is a chronic inflammatory disease of probable immune-based etiology. The pathogenesis of LP is unclear, but apoptotic changes in epidermal (epithelial) cells have been reported. Destruction of the basal cell layer is observed and many changes in cell proliferation, cell repair and cell death occur in the injured mucosal epithelium. The aim of this study was to evaluate and compare the expression of bax and bcl-2 in oral lichen planus (OLP), well differentiated oral squamous cell carcinoma (WOSCC) and normal mucosa. Sixty one paraffin-embedded biopsy including 11 cases of WOSCC, 30 cases of OLP (n=15 erosive OLP [OLP-E], n=15 reticular OLP [OLP-R]) and 20 normal mucosa were entered in our research. We used immunohistochemistry staining method for assessing bax and bcl-2 expression in epithelial layers. The percentage of stained cells was estimated in 5 randomized microscopic fields and classified as (-): 0%, (+) :< 10%, (++): 10-25%, (+++): 26-50%, (++++): > 50% positive cells. The data were analyzed with Mann-Whitney, Chi Square, and Kruskal-Wallis tests. Significant differences in bax expression were observed among OLP, WOSCC compared to normal mucosa (P=0.008). No significant difference in bax expression between OLP-E and OLP-R compared to WOSCC was seen (P>0.05). Bcl-2 was negative for all OLP and normal mucosa samples, and weak positivity was observed in WOSCC samples. According to the findings of our study, it may be possible to correlate the difference of bax and bcl-2 expression levels among the mentioned lesions to the malignant potential of OLP.

immunohistochemical studies strongly support an immunologic basis for the disease (2). The potential form alignant transformation of OLP, especially erosive type remains controversial.
In 1999, Van  into oral squamous cell carcinomas (6). Some authors believe that most malignant transformed cases described in the literature, have not been sufficiently documented to be described as such (3,(7)(8). Several studies have suggested that OLP has a malignant potential and the rate of malignant transformation in OLP has been estimated to be 0.4-6.25% (9-10). However, other studies failed to prove the malignant transformation potential of OLP (3,11).
Apoptosis is a programmed cell death which is induced by cell damage beyond repair, viral infection or stress conditions such as starvation.
Apoptosis can be caused by the cell itself, the surrounding tissue or inflammatory cells (12). The triggers for apoptosis in OLP are still unknown, but T cells attack to basal epithelial cells triggers a series of complex molecular mechanisms designed to arrest the cell cycle for DNA repair, induce cell senescence or apoptosis to eliminate cells with severely damaged DNA (13). However, some authors demonstrated that epithelial cells in OLP frequently respond to this attack with an increase in cell proliferation rate (14)(15)  not only for their known key role in these processes but also for the participation in the human carcinogenesis process especially in oral cavity (16). Detection of apoptotic abnormalities before the consequences become clinically or histologically detectable will greatly help the early diagnosis.
The increase in expression of bcl-2 is not only essential for oral carcinogenesis, but also influences the progression of the disease. Because it increases the survival rate of neoplastic cells, allowing new genetic mutation to occur and granting their higher resistance to chemotherapy and radiotherapy (6,17). Considering the importance of bcl-2 and bax in apoptosis, and because few researches have evaluated the role of these apoptotic markers in malignant changes of OLP, the aim of this study was to evaluate and compare the expression of bax and bcl-2 in OLP, WOSCC and normal oral mucosa.

Samples
A total of sixty paraffin-embedded biopsy samples with diagnosis of OLP and OSCC were  (19).

Statistical analysis
SPSS Version 18.00 was used for statistical analysis. The data were analyzed using the Mann-Whitney, Chi-Square, and Kruskal-Wallis tests.

Results
Significant differences in bax expression were observed among OLP and WOSCC compared to normal mucosa (P=0.008). No significant difference in bax expression was seen between OLP-E and OLP-R compared to WOSCC (P=0.138 and P=0.206, respectively) (Fig. 1).
There was no significant difference in bax expression between OLP-E and OLP-R (P=0.91).
Bax expression in OLP was significantly higher than normaloral mucosa (P=0.007), but no statistically significant difference between OLP and WOSCC in bax expression level was seen (P=0.089) ( Table 1) (Fig. 2, 3). No expression of bcl-2 was seen in OLP and normal mucosa samples.

Discussion
During  even if the process were brief and some cells did not show their nuclei (13,24,36 Authors declare no conflict of interest.